Smokeless powder



Patented Nov. 11, 1930 UNITED STATES PATENT OFFICE FRANCIS I. no ZPONT, or wrnmme'ron, DELAWARE, AssIeNoa. r0 u. s. r. rownan comrun, or wrnmmeron, DELAWARE, A coaroaarroiv or DELAWARE SMOKELESS POWDER No Drawing.

My invention relates to an improved smokeless powder, such as is used in guns of various types, and more particularly relates to the provision of a powder which will be less sensitive to the effect of the final dryingprocess to which it is submitted in the process of manufacture.

In the manufacture of smokeless powder, such as is used in this and most other countries, the pellets or grains are produced by dissolving nitrocellulose in a mixture of ether and alcohol, forming the mass into the desiredshape by pressureand then drying the formed rains.

When the grains of powder, after their formation, are subjected to the drying process they contain'about one-third of their total weight of ether, alcohol and a small amount of water, the water being present due to the impossibility of completley eliminating water from the alcohol used, and to other causes.

The drying process consists in subjecting the powder grains to a current of air at a temperature of abut C. The heated air first "causes substantially all of the ether to go off, taking with it a part of the alcohol. Then almost all of the remaining alcohol oes off, taking with it a part of the water. Vhen the drying operation is completed the powder will contain some alcohol, a little ether and some moisture.

If the powder on completion of the drying operation were immediately tested, it would be found that the results obtained would be at variance with results obtained from test of the powder after it had been in storage for a time. The reason for the variance is apparently that the powder takes up moisture in storage, even when precautions are taken against undue exposure to the atmosphere of the powder in storage.

In practice it has been found best to allow the powder, after the final drying operation and before storage, to remain exposed to the Application filed October 29, 1926. Serial No. 145,102.

air for a period of a few days, during which a certain amount of moisture is taken up. The powder, after such exposure, is found to be in more stable equilibrium and less subject to change under the usual condition of handling and storage.

The moisture taken up by the powder during theperi'od of exposure is disadvantageous, since it aifects the ballistics of the powder, but since the taking up of some moisture, by freshly dried powder, is inevi table, even when stored under ideal conditions, it has been found best to facilitate the absorption of moisture under known conditions, rather than have it occur under unknown conditions of humidity and tem eratures with corresponding unknown e ect upon the ballistics.

In the drying operation care must be used to permit a certain amount of the solvent to remain in the powder, since long experience has indicated that a certain amount of residual solvent, principally alcohol, in the powder is necessary to the proper function'- ing of the powder in a gun.

f the powder be excessively dried, that is, if such an amount of residual solvent as obtains in the best practice be not left in the powder, and the powder be allowed to take on moisture to such an amount as will bring the total volatiles to the same percentage as is found in powder normally prepared,

the powder will exhibit in practice what 15 known as .a dangerous pressure curve, that is, when the pressures and velocities in the firing test-are plotted for increasing weights of charge, the pressures will increase after a certain point much faster than the velocities.

The presence in the powder of a few percent of residual solvent apparently avoids the dangerous pressure curve, due, I believe, to the presence of thecarbon and hydrogen in the residual solvent.

In an effort to insure against the proaddition to the usual solvents for the nitrocellulose, another solvent less volatile than the alcohol be added, but such has not proved successful, since the presence of a less volatile solvent renders it more diiiicult to eliminate the solvents to the desired point, with the result that the powder produced is much too slow.

Now, in accordance with my invention, I have found that if there is added to the solvent for the nitrocellulose a substance miscible therewith, liquid at atmospheric temperatures and which contains carbon and hydrogen in about the proportion contained in alcohol, and which is not volatile at the temperatures used in manufacture and storage of the powder, and which is not a solvent of the nitrocellulose, that the powder will be greatly improved.

In accordance with my invention, I treat nitrocellulose with the usual colloiding agents or solvent, as alcohol and ether, and I add a substance miscible with the colloiding agents or solvent and with water, having about the same proportions of carbon and hydrogen as has the alcohol, having no solvent or colloiding power on the nitrocellulose and being non-volatile at-the temperatures used for drying the powder. As an example of a substance such as I add to the colloiding agents for the production of a powder in accordance with my invention, I would mention glycerine, C ll OH) with the use of which I have foun may be produced a greatly improved powder.

In the production of the powder in accordance with my invention, for example, there is added to the colloiding solvent, which may he the usual mixture of alcohol and ether, an amount of glycerine equal to say from 1%-5%, by weight, of the nitrocellulose to be treated. The nitrocellulose is colloided by treatment with the colloiding solvent and glycerine, formed into grains and dried, in any usual form of apparatus and in the usual manner.

The powder, when dry, will contain the glycerine, which will not be evaporated at the temperatures, not above (1., used for driving 05 or evaporating the alcohol and ether, and owing to the fact that the percentages of carbon and hydrogen in the glycerine are not greatly different from those in alcohol, the

presence of the glycerine will. insure to a certain extent against the powder being dried to a point where a dangerous pressure curve ap pears.

Q The presence of the glycerine insures to a certain extent against changes in the moisture content of the powder, due to conditions of and handling, since in mixtures of cerine a 7 water there are certain proporions which ive a stable mixture which g changes very little when exposed to either moist or dry air which proportions are reached and a stable mixture of glycerine and residual moisture automatically formed in the drying operation. The stable mixture is formed due to the fact that the glycerineis somewhat hydroscopic and absorbs moisture of the air. lVhen there is a certain percentage of moisture present in the glycerine the hydroscopic properties of the glycerine are satisfied and it does not lose this moisture by ordinary methods of evaporation so that there is no tendency for the percent of oisture to increase or decrease with ordinary changes of atmospheric moisture.

The glycerine, since it has no solvent power on the nitrocellulose, and hence does not take part in the dissolving of the nitrocellulose, does not in the least hinder or interfere with the removal of the solvent from the powder to the desired extent in the drying operation. Further, since the glycerine is non-volatile at the drying temperature, the amount desired to be present in the finished powder can be fixed to a nicety by merely introducing into the solvent, or mixing with the nitrocellulose, the exact amount desired.

While I have described my invention in connection with the use of glycerine, it will be understood that my invention contemplates the use of other substances having the characteristics indicated herein and capable of producing the results described.

Having -now fully described my invention, what I claim and desire to protect by Letters Patent is 1. A propellant powder including colloided nitrocellulose in dominating proportion and a substance substantially nonvolatile at a normal temperature for drying of powder, which is non-solvent of the nitrocellulose, which is liquid at atmospheric. temperatures, which contains carbon and hydrogen and which is soluble in and will form a substan tially stable mixture with water.

2. A propellant powder including colloided nitrocellulose in dominating proportion and a substance substantially non-volatile at normal temperatures for drying of powder, which is liquid at atmospheric temperature, which contains carbon and hydrogen in about the proportions contained in alcohol, which is non-solvent of the nitrocellulose and which is soluble in and will form a substantially stable mixture with water.

3. A propellant powder including colloided nitrocellulose in dominating proportion, residual solvent and a substance substantially non-volatile at normal temperatures for drying of powder, which is liquid at atmospheric temperature, which contains carbon and hydrogen in about the proportions contained in alcohol, which is non-solvent of the nitrocellulose and which is soluble in and will form a substantialiy stable mixture with water 4. A propellant powder including colloided nitrocellulose in dominating proportion and glycerin.

5. A propellant powder including colloided nitrocellulose in dominatingv proportion and glycerin in amount from 1-5% by weight. w

6. A propellant powder including colloided nitrocellulose in dominating proportion, residual solvent and glycerin.

In testimony of which invention, I have hereunto set my hand, at Wilmington, Delaware, on this 26th day of October, 1926.

FRANCIS I. DU PONT. 

